//is用来比较两个值是否完全相等  ===

console.log(Object.is('foo','foo'));
console.log(Object.is(global,global))
console.log(Object.is({},{}))
//一般来说可以认为Object.is和===效果相同
console.log(NaN===NaN)//false
console.log(Object.is(NaN,NaN))//true

console.log(+0===-0)//true
console.log(Object.is(+0,-0))//false